The invention relates to an airbag module for motor vehicles having a housing for an inflatable airbag and a gas generator.
Such airbag modules serve to receive the airbag in the folded state and to inflate it by means of the gas generator in the case of a crash. The airbag modules are installed in the vehicle as a unit. It is a problem, in particular with driver airbags to be installed at the steering wheel, that vibrations which occur during the operation of the vehicle can be transmitted to the steering wheel unit and thus to the airbag module.
It is the underlying problem (object) of the invention to provide an airbag module of the kind initially mentioned which has as simple a construction as possible and which is not impaired by vibrations which occur and which can be used in particular as a driver airbag which can be integrated into a steering wheel unit.
This object is satisfied by the features of claim 1 and in particular by the gas generator being connected to a base element fixed to the module in the assembled state, with the gas generator and the base element being combined to form an assembly serving as a vibration absorber and being unreleasably connected to one another by at least one elastic and/or vibration damping coupling element via which the gas generator is supported over its area at the base element.
In accordance with the invention, the gas generator, which has a comparatively large mass, is used as a vibration damper. It is of particular advantage that the gas generator and the base element, which form the vibration absorber assembly together with the coupling element and which are unreleasably connected to one another by the coupling element, are used as a unit and can be commonly integrated into the module when the airbag module is assembled. The manufacture of the airbag module is made substantially simpler in this way. In particular, additional measures to hold the unit of gas generator, base element and coupling element together are superfluous due to the unreleasability of the connection made between the gas generator and the base element by the coupling element. The areal support of the gas generator means that the coupling element serves as an elastic and/or vibration damping base component, i.e. the base element and the coupling element jointly form a base assembly for the gas generator which is able to damp or decrease vibrations. Furthermore, the stress of the coupling element with respect to a coupling element formed, for example, as an elastic suspension can be reduced by the coupling element serving as a support for the gas generator. Damage to the coupling element caused in particular by material fatigue can be prevented in this way in accordance with the invention. It is moreover of advantage that the installation procedure and the installation position of the assembly with respect to a fixed tying of the gas generator practically do not need to be changed due to the invention.
It is particularly preferred if the base element, the coupling element and the gas generator at least regionally form a sandwich-like assembly.
In a further practical embodiment of the invention, it is provided that the coupling element is vulcanized both to the gas generator and to the base element.
This connecting of the coupling element to the gas generator and to the base element, which is free of securing means, but which is nevertheless stable and secure, allows a simple manufacture and handling of the vibration absorber. Moreover, in this way, a gas-tight connection of the gas generator to the base element and thus to the airbag module can be simply ensured with the coupling element.
The coupling element consists for example of rubber or a rubber-like material.
In accordance with the invention, other materials can generally be used for the coupling element and/or in particular different ways of securing the coupling element to the gas generator and to the base element can be used.
It is particularly preferred for the coupling element to have a higher stiffness parallel to a longitudinal module axis than perpendicular to the longitudinal module axis. This embodiment is in particular advantageous for airbag systems which can be integrated into steering wheel units.
In accordance with a further preferred embodiment of the invention, the coupling element has a closed peripheral contour and is in particular of an annular shape.
The coupling element can simultaneously carry out a plurality of functions by this embodiment in that it, on the one hand, provides an elastic connection of the gas generator to the base element and, on the other hand, ensures the gas-tightness between the gas generator and the base element.
In a preferred variant of the invention, the coupling element can have a wall thickness which varies in the peripheral direction. A particularly preferred embodiment provides that the coupling element has contact regions with a relatively large wall thickness distributed in the peripheral direction and sealing regions with a relatively small wall thickness between the contact regions, with the contact regions, which serve as elastic coupling bases and, for example, have an at least approximately circular or semi-circular contact area, providing a sufficient stability and stiffness of the connection, while the wall regions extending between these contact bases substantially carry out a sealing function. The coupling element and thus the absorber assembly can be directly matched to the respective demands by a corresponding dimensioning, in particular of the contact regions.
In a particularly preferred embodiment of the invention, the coupling element is formed as a radial vibration limiter for the gas generator, with the coupling element not only serving for the support of the gas generator at the base element, but simultaneously fulfilling a vibration limitation function in the radial direction. Additional measures such as separate vibration limiters are hereby not necessary. The manufacture of the airbag module can be substantially simplified in this manner since care only has to be taken for the connection of the coupling element to the gas generator and to the base element and in this manner care is already taken for a secure support of the gas generator at the base element and a limitation of radial vibrations of the gas generator, or vibrations of the gas generator perpendicular to a longitudinal module axis, is also ensured.
It is preferred for the coupling element and the gas generator to mutually overlap in the axial directionxe2x80x94with respect to a longitudinal module axis. In this respect, the gas generator can contact the coupling element directly in an areal manner in the radial direction, with preferably a radially outer surface of the gas generator being fixedly connected, in particular by vulcanization, to the coupling element or to a radially outwardly lying section of the coupling element.
In accordance with a particularly preferred practical embodiment, the gas generator is inserted into the coupling element and is surrounded at least regionally by the coupling element. A particularly stable connection is hereby realized between the gas generator and the coupling element.
It is particularly preferred for the coupling element to be formed in step shape at least regionally for the simultaneous axial and radial support of the gas generator.
The coupling element can have a peripheral support step for the gas generator at its radial inner side.
The gas generator can be placed onto a step-shaped section or a support step of the coupling element and can simultaneously be fixedly connected to the coupling element, in particular by vulcanization, via a lower and a radially outer or inner surface.
The coupling element preferably has two annular sections radially offset with respect to one another in order to form a support step for the gas generator.
It is further proposed for the coupling element to have reinforcement regions distributed in the circumferential direction in which the wall thickness of the coupling element is enlarged in comparison with regions disposed between the reinforcement regions in particular in the region of an upper and/or of a lower annular section.
The gas generator can have a collar for the support of the coupling element which is preferably formed at least approximately in a U shape in cross-section.
It is preferred in this respect for the collar to be arranged in a manner radially outwardly offset and in particular to merge via a step-shaped transition section into a side wall of the gas generator which preferably extends axially.
In accordance with a further preferred embodiment of the invention, at least one preferably separate vibration limiter is additionally provided for the gas generator and is preferably made of an elastic material. The vibration limiter can have a greater stiffness than the coupling element at least perpendicular to a longitudinal module axis. A plurality of such vibration limiters are preferably provided.
Relative movements between the gas generator and the base element, which the coupling element permits due to its design, can be limited by the vibration limiter(s). The coupling element can thereby be optimized with respect to its vibration damping function without having to meet any certain marginal conditions with respect to protection due to possible movements of the gas generator. In particular, such relative movements can be suppressed by the additional vibration limiters where, without this preferred embodiment of the invention, the danger would arise that the coupling element would be released from the gas generator or from the base element or that the coupling element would tear.
The vibration limiters are preferably formed with a pin shape and preferably extend approximately parallel to a longitudinal module axis of the gas generator.
It is furthermore preferred for the vibration limiters each to be fixed at the base element with one end and to engage into a recess of the gas generator with another.
The invention moreover relates to a method for the manufacture of an airbag module for motor vehicles comprising a housing for an inflatable airbag and a gas generator in which an assembly serving as a vibration absorber is manufactured by a coupling element being unreleasably connected both to the gas generator and to a base element and by the assembly being integrated into the airbag module as a unit.
Further improved embodiments of the invention are also given in the dependent claims, the description and the drawing.